Omega OMB-DAQBOARD-500 User Manual

2-10    Connections & Pinouts 

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DaqBoard/500 Series User’s Manual 

Floating Signal Sources are typically wired to a data acquisition board in Single-Ended configuration.  However, 
when the Floating Source signal leads pass through an electrically noisy environment, Differential configuration 
will give the best performance.  
 
When wiring Floating Signal sources in Differential configuration, a resistor can be connected from the low side of 
the sources to analog ground (AGND). These resistors create a return path to AGND for the bias currents of the 
instrumentation amplifier and can reduce the common mode noise. 
 
All DaqBoard/500 Series boards provide 10 M

Ω of resistance between each analog input and ground.  

Ω of resistance is sufficient for the return of bias current. 

 

Use a Resistor Value from:  10 K

Ω to 100 KΩ 

  Use resistors with values from:  10 K

Ω to 100 KΩ 

Connect the resistor between: 

  (a) Connect one resistor between: 

  Input Signal Return (ARET) and AGND 

   

Input Signal High and  Input Signal Low 

   

  (b) Connect a second resistor between: 

Input Signal Low and AGND 

Making resistor connections as indicated will significantly increase the load on the measurement source, possibly 
reducing the measured voltage.  A trial and error approach may be required when trying to reduce common mode 
noise. 
 
 
The following figure shows how to properly wire a Floating Source Signal in Differential configuration.